This invention relates to a tractor having an arrangement for increasing the vehicle speed, and more particularly, relates to the use of the tractor PTO mechanism to obtain a high vehicle speed.
Currently marketed tractors are normally designed for a maximum speed of about 40 km/h, which is not normally exceeded to avoid impairing the on-road stability of the tractor, especially when an implement is attached.
There are times, however, when a higher speed is desirable, particularly in the case of wheeled tractors traveling frequently along asphalt roads, to prevent slowing down other road users.
Some solutions currently adopted to increase maximum tractor speed consist in equipping the transmission with gears designed to achieve the desired velocity ratios, which obviously increases the production cost and overall size of the transmission.
Other solutions concentrate directly on the bevel pinion/ring gear velocity ratio. This, however, results in an increase in all the speeds supplied by the transmission, which, in most cases, is unacceptable.
Other known solutions consist in a transmission comprising two subsystems: a first for achieving a given speed range, and a second for achieving higher speeds up to a maximum of 50 km/h. The outcome, however, is a highly complex transmission.
Moreover, full market coverage would mean producing and marketing tractor models with maximum 40 km/h transmissions, and others with 50 km/h transmissions, thus greatly increasing storage costs.
It is an object of the present invention to provide a vehicle, in particular a tractor, designed to eliminate the aforementioned drawbacks.
An inventive solution has been devised by which the device transmitting power to the rear power take-off (PTO) of the tractor is employed to achieve a velocity ratio in some way complementary to those obtainable with a conventional transmission.
As opposed to high-cost alterations to existing transmissions, the solution according to the present invention involves only minor mechanical alterations to the engine-PTO power transmission device, which remains substantially unchanged as a whole.
According to the present invention, there is provided a vehicle comprising a frame, an engine, a transmission for selecting a number of vehicle speeds, and a device for transmitting power from the engine to a PTO; the vehicle being characterized by comprising means forming part of the device for transmitting power from the engine to the PTO, and by which to select a vehicle speed higher than any speed selectable by means of the transmission.
These and other objects, features and advantages are accomplished according to the instant invention by providing a tractor having a frame, an engine, a transmission for selecting a number of vehicle speeds, and a device for transmitting power from the engine to a PTO mechanism. The tractor has a mechanism forming part of the device by which the tractor speed can be selected to be higher than any speed selectable by means of the transmission.